Plumb control for horizontal boring drilling and milling machine



Dec. 16. 1969 c. F. KOENIG m 3,484,064

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PLUMB CONTROL FOR HORIZONTAL BORING DRILLING AND MILLING MACHINE Filed July 12, 1967 4 Sheets-Sheet 4 INVENTOR CARL 5120 K0 ENI ZZX ATTOR N EYS United States Patent 3,434,064 PLUMB CONTROL FOR HORIZONTAL BORING DRILLING AND MILLING MACHINE Carl Fred Koenig III, Montgomery, Ohio, assignor to G. A. Gray Company, Hamilton County, Ohio, a corporation of Ohio Filed July 12, 1967, Ser. No. 652,806 Int. Cl. Fl6m 11/00 Cl. 248I3 17 Claims ABSTRACT OF THE DISCLOSURE A machine tool has a vertical tool carrying column with a base which is slidable carried on a saddle which is also slidable carried on ways on the machine tool support. Hydrostatic bearing shims are provided on one side of the column between the column and column base, or the column base and saddle, or the saddle and the ways and are controlled by a sensor, carried on the column, which senses minor deviations of the column from the vertical in order to cause lifting of one side of the column to return it to true vertical. A pair of sensor and hydrostatic lifting bearing arrangements may be used arranged perpendicular to each other to position the column in two directions.

BAQKGROUND OF THE INVENTION Modern machine tools must produce parts to a degree of precision unheard of just a few years ago. The requirements of the aero space industry, the automotive industry and others have produced a new generation of machine tools in which entirely new design and manufacturing techniques are necessary to obtain the required accuracy. In addition to designing much greater strength into machine tool components, and to manufacturing these components to more exact dimensions, it is often necessary to incorporate adjusting devices which compensate for very small transient errors occuring in the machine during operation.

This invention has great and particular utility in connection with large horizontal boring, drilling, and milling machines. In this type of machine, the cutting tool, spindle, and driving head are carried on a very large vertical column. This vertical column will generally be secured to a column base. The column base is slidably carried by a saddle, which is in turn slidably carried by a runway which supports the entire machine and rests on a reinforced concrete foundation.

There are several sources of error in the location of the tool on this type of machine;

(1) Each axis of motion involves one member sliding on another with possible inaccuracies at sliding joints.

(2) The runway and saddle structure through which the weight of the column and driving head are supported from the foundation is not uniform at all positions of the tool, particularly during the cross travel motion of the column on the saddle.

(3) The entire machine is supported from a reinforced concrete foundation which is frequently subjected to some deflection under the large weights imposed by this type machine.

(4) Temperature gradients in various elements of the machine may be created by sunlight, local drafts, and even by continued operation of the machine. These gradients cause unequal expansions of components and relative motion between them.

inaccuracies resulting from the above several causes are particularly disturbing where they result in deflections of the column from its true vertical alignment. A very small distortion in for example the saddle will be magnified "ice several times in terms of movement of the cutting tool. Because of this magnification factor, it has been found to be impracticable to design the runway and saddle components to have sufficient rigidity that some small deflection of the tool does not occur. Furthermore, the deflection of the foundation and the differential expansion of machine components due to temperature gradients are usually not predictable. It becomes imperative, then, that compensating features be incorporated to correct the vertical alignment of the column continuously during operation.

SUMMARY Generally considered, this invention contemplates the provision of level sensing means associated with the vertical column and arranged to detect level error, and column tilting means operative in response to a level error detected by the sensing means to tilt the column into true vertical alignment.

According to the preferred embodiment of the invention, the tilting of the column into true vertical alignment will be accomplished hydrostatically. That is, means are provided wherein the quantity of fluid supplied to certain hydrostatic pads can be varied so as to effect a very slight tilting of the column sufiicient to bring it into true vertical alignment. In one embodiment of the invention, the tilt correction is accomplished by means of a hydrostatic shim, disposed between one edge of the columnand the column base, while in a second embodiment of the invention, the tilt correction is accomplished by providing hydrostatic bearings between for example the saddle and column base, and varying the quantity of hydraulic fluid supplied to certain of those bearing pads in order to accomplish the tilt correction.

DESCRIPTION OF THE DRAWING FIGURE 1 is a perspective view showing a horizontal boring, drilling and milling machine to which this invention can advantageously be applied.

FIGURE 2 is a partial cross-sectional view through one edge of the column flange and showing a hydrostatic shim.

FIGURE 3 is a horizontal plan view showing a plurality of hydrostatic shim pads under one column flange.

FIGURE 4 is a partial cross-sectional view similar to FIGURE 2 but showing a modification of the hydrostatic shim.

FIGURE 4a is a fragmentary view on an enlarged scale of a portion of FIGURE 4.

FIGURE 5 is a crosssectional view similar to FIG- URE 4 showing still another modification of the invention.

FIGURE 6 is a plan view showing the arrangement of a plurality of hydrostatic bearings.

FIGURE 7 is a partial cross-sectional view showing a single adjustable hydrostatic bearing.

FIGURE 8 is a partial cross-sectional view similar to FIGURE 7 showing a modification of a single hydrostatic bearing.

FIGURE 9 is a partial cross-sectional view showing a further modification of a single hydrostatic bearing.

FIGURE 10 is a plan view showing another arrangement of hydrostatic bearings for accomplishing the adjustment of this invention.

FIGURE 11 is a schematic diagram showing a control circuit for the hydrostatic shim.

FIGURE 12 is a schematic diagram showing the fluid control circuit for the modified hydrostatic shim illustrated in FIGURE 5.

FIGURE 13 is a schematic diagram illustrating the fluid control circuit for a plurality of hydrostatic bearings such as contemplated in FIGURE 6.

3 FIGURE 14 is a schematic view of the fluid control circuit for the hydrostatic bearings illustrated in plan View in FIGURE 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIGURE 1 is a perspective view of a typical large horizontal boring, drilling, and milling machine. A cutting tool will be mounted on the end of a cylindrical spindle 12 which is carried by the driving head 14. The head 14 is mounted on vertical ways 16 on the large column 18, and is moved up and down these ways by the vertical screw 20. The column 18 is mounted on the column base 22, which may be moved in a direction parallel to the spindle axis on ways 24 which support the column base 22 on a saddle 26. The saddle 26 may be moved along the ways 28 in a direction perpendicular to the spindle axis on a runway 30, which supports the whole machine and rests on a reinforced concrete foundation.

In order to give some indication of the order of size of such a machine, the cross travel of the column 18 on the ways 24 may vary from 24 inches to 72 inches, and the column travel along the ways 28 may vary from 6 feet to 40 feet Or more. It is in part the large size of these dimensions which led to the instant invention. That is, it is impossible to design a tool of this magnitude with suflicient rigidity to prevent small deflections permitting the column to get out of true vertical alignment. Therefore, it is necessary to provide means for continuously sensing and compensating for vertical misalignment due to any cause during operation.

For clarity of description, transverse column tilting will be defined as tilting in a plane parallel to the spindle axis, and longitudinal column tilting as tilting in a plane perpendicular to the spindle axis. It will also be noted that the standard observer orientation (right, left, front, rear) used in describing this machine is illustrated in FIGURE 1.

One way to correct the vertical misalignment of the column is to provide a lifting device between one edge of the column 18 and the column base 22. According to the preferred embodiment of the invention, this adjustment is accomplished by a hydrostatic shim, as illustrated in cross-section in FIGURE 2. It will be noted in this figure that the column 18 includes an outwardly extending column flange 18a which overlies a portion 22a of the column base. According to this invention, a shim plate 32 will be suitably secured to the column base 22a in a position underlying the flange 18a. Secured to the upper surface of the shim plate 32 will be a suitable block 34 which is provided on its upper surface with a plurality of recesses 36.

FIGURE 13 shows in plan view the arrangement of a plurality of recesses 36 in the block 34. It will be noted that each recess is provided with the passages 38 and 40 which communicate with a supply of high pressure oil to be described hereinafter.

Surrounding all of the recesses 36 will be a drain groove 42 which communicates through conventional passages with a reservoir in the oil supply system. 2

Finally, surrounding the drain grooves 42 is the dirt seal 44. These seals can be of any suitable material, and simply serve to keep dirt and the like out of the hydrostatic shim system.

The control for this hydrostatic shim is schematically shown in FIGURE 11. 46 is an electronic level sensor of conventional design which is associated with the column 18 as shown in FIGURE 1 so as to produce a signal indicating the presence of level error. This signal may be amplified as at 48 and sent to an electro-hydraulic controller 50 which actuates a variable flow control valve 52.

Hydraulic oil for the hydrostatic system is contained in a reservoir 54. The pump 56 draws oil from the reservoir 54, pumps it through the cooler 58 and filter 60 to the flow control valve 52 previously menti Jll t-i. The relief valve 62 is disposed a short distance up stream or the flow control valve 52, and serves to limit the pressure in the system. The hydraulic oil passing the flow control valve 52 goes directly to the passages 40 and 38, and into the recesses 36 previously described. Similarly, as indicated in this figure, the drain grooves 42 will be connected to the reservoir 54 by suitable passages.

In operation, high pressure oil is supplied to the recess 36 at a controlled flow rate. This oil leaks out in all directions from the recess and is collected in the drain grooves 42. A lifting force equal to the average pressure over the bearing pad area, multiplied by the pad area is applied to the column flange 18a. A proper combination of oil pressure, oil flow and pad area lifts the column so that it floats on a thin film of oil at all times.

There is a self-compensating action in this arrangement in that any tilt in the column which increases the distance between the column flange and the column base also increases the leakage area between the recesses and the drain groove, and thereby lower the pressure and lifting forces across the flange. On the other hand, if the column tilt decreases the distance between the column flange and the column base, the leakage area decreases with a consequent increase in pressure and lifting force.

It will be understood that to raise or lower the column flange 18a, it is only necessary to adjust the flow rate of oil being delivered to the recesses 36. An increased flow of oil requires a larger leakage area, hence will raise the column flange 18a. Similarly, a reduced flow of oil lowers the column flange.

In extreme situations, where the column lift required is relatively large, a balanced seal arrangement such as shown in FIGURE 4 may be added to provide a higher lift but keep the quantity of oil required within reasonable limits. In this embodiment, the block 64 is provided with a recess 66 having a shoulder 66a. This shoulder is provided with the annular wedge groove 68.

The seal ring 70 includes a wedge 72 designed to mate with the wedge groove 68, and carries on its opposite surface the sealing member 74. The sealing ring 70 is generally biased toward the under surface of the column flange by means of the calibrated springs 76.

During operation, the hydraulic fluid entering the system through the passage 78 will exert equal forces on opposite sides of the seal ring 70. Therefore, the only force between the sealing member 74 and the underside of the column flange is that exerted by the springs 76. The clearance through which the oil leakage passes is equal to the vertical lift e of the seal ring 70 multiplied by the sine of the wedge angle 6. Obviously, the angle of the wedge can be varied as desired to alter the lift-leakage ratio as necessary. The lift from this version of the hydrostatic shim is controlled by varying the oilflow, in the same manner as described in connection with FIGURE 11.

For extreme applications, particularly where high-grain numerical control systems are involved, the rigidity of the overall machining system must be extremely high and a more positive anchoring force is required on the flange of the column than the weight of the column alone. In this case, an opposed pair of hydrostatic shims such as illustrated in FIGURE 5 is used.

Generally considered, this arrangement provides hydrostatic pressure pads both above and below the column flange so that large forces are exerted in both directions whenever the oil pressure is appleid. The areas of the two pads are proportioned so that the column flange floats between the two pads with approximately equal clearance on each side. To alter the tilt of the column, the oil flow is simultaneously adjusted to both the upper and lower pads so that the neutral position of the column flange is raised or lowered the desired amount.

In this particular arrangement, the column flange 18b must be machined on both surfaces. The hydrostatic shim block 80 is arranged to have a portion under the flange 18b, as Well as a second portion over the flange 18b. It

will be noted that the shim block 80 carries a number of recesses 82 which will be under the flange 18b, and a plurality of somewhat smaller recesses 84 which will be on top of the flange 18b. These recesses are supplied with oil through the passages 86 and 38 respectively. Leakage from the recesses 82 and 34 will be collected in the drain grooves 90, 92 and 94.

The control system for this arrangement is illustrated schematically in FIGURE 12, and again includes the electronic level sensor 46 and amplifier 48 which detect level error and via the electro-hydraulic controller 59 control the flow of hydraulic oil to the system. In this system, the electro-hydraulic controller 50 controls both the variable fiow control valve 52 as well as the reverse-acting variable flow control valve 52a. It will be observed that the other components of the system are substantially the same as that described in connection with FIGURE 11.

It will be recognized that the opposite acting flow control valves 52 and 52a will serve to increase the flow to one hydrostatic pad at the same time the fiow to the other hydrostatic pad is decreased.

While all of the foregoing disclosure has been in terms of uni-directional column tilting, it will readily be understood that all of the specific systems discussed can be duplicated to provide tilt correction in both the longitudinal and transverse planes. It will be understood tha the electronic level sensor 46 shown in FIGURE 1 can be arranged to detect level error in two places, or a second sensor can be provided on a side of the column adjacent to the one carrying the sensor 46 shown in FIGURE 1.

It will further be obvious that the hydrostatic shims discussed above are disposed between two relatively stationary members, the column and the column base. It is also possible to accomplish the desired column tilt by the use of hydrostatic bearings either between the saddle and the column base, or between the runway and the column base. In either of these arrangements, the usual sliding bearings are replaced by hydrostatic bearings. FIGURE 6, for example, shows in plan view an arrangement of hydrostatic bearings between the column base 22 and the saddle 26. Bearings A, B, and C on each of the three ways would be conventional hydrostatic bearings supplied with high pressure oil through a constant flow controller. Bearings D and E for each way would be supplied with oil through variable flow control valves which are actuated by a level error signal as described earlier. The elevation of the column base may be changed by changing the flow to these hearings. FIGURE 6 shows that there is some space between bearing E and the right end of the ways to allow for column cross travel. A normal non-metallic bearing is used in this area.

By way of illustration, bearing E on way III is shown in cross-section in FIGURE 7. It will be apparent that the operation of this hearing is substantially identical to that of the single hydrostatic shim shown in FIGURE 2 and described earlier. Accordingly, similar reference numerals have been used.

It will be apparent that the hydrostatic bearings utilized to control column tilt may be fitted with a balanced seal, as illustrated in FIGURE 8, to provide a higher lift in these hearings without an excessive increase in oil flow. Again this balanced seal bearing is substantially identical in operation to the balanced seal hydrostatic shim illustrated in FIGURE 4 and described earlier; again, similar reference numerals have been used in this figure.

And finally, there are instances where extreme rigidity of the assembly requires opposed hydrostatic bearings. FIGURE 9 illustrates in cross-section the details of an opposed hydrostatic bearing. This opposed bearing is substantially the same as the opposed hydrostatic shim shown in FIGURE 5 and described earlier. And, again, similar reference numerals have been used.

The control system for the hydrostatic bearing system of FIGURE 6 is schematically shown in FIGURE 13. The level sensor 46, the amplifier 48, and the electrohydraulic controller 5b are the same as described previously. Similarly, the oil supply system consisting of the reservoir 54, pump 56, cooler 58, filters 60 and relief valves 62 is the same as described earlier. Flow control valves 96 are self contained devices which maintain a constant fiow rate under all conditions. Variable fiow control valves 52 supplying bearings D and E are actuated by the level sensor to increase or decrease the quantity of fiow to these hearings, and hence, to raise or lower the column base as desired.

FIGURE 10 shows in plan view the arrangement of hydrostatic bearings as used between the saddle 26 and the runway 3%. To control transverse column tilt, the bearings on ways 1 and 2 are conventional hydrostatic bearings, supplied with a constant flow of oil to each bearing. The hearings on ways 3 and 4 are supplied with a variable flow of oil which is changed to raise or lower the saddle as well as the column base and column, as required to maintain the true vertical alignment of the column.

The control system for this arrangement is schematically shown in FIGURE 14. It is substantially the same as that shown in FIGURE 13, and similar reference numerals have been used to designate the components.

It will also be understood that the bearings between the column base and the saddle illustrated in FIGURE 6 may be controlled to correct tilt in a longitudinal direction rather than in a transverse direction. In this case, all of the bearings on way III could be controlled to raise or lower the rear edge or the column and thus provide longitudinal tilting correction. Similarly, with respect to the bearing arrangement shown in FIGURE 10, all of the bearings N could be controlled to provide longitudinal tilting correction.

Generally speaking, it will be desirable to provide both longitudinal and transverse tilting corrections; and to this end, various combinations of the systems discussed above may be selected.

While the invention has been described in terms of several specific exemplary embodiments, numerous changes and modifications should be apparent to the skilled worker in the art.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a machine tool having a vertical column, a column base carrying said column, a saddle having a plurality of transverse ways slidably carrying said column base, and a runway having a plurality of longitudinal ways slidably carrying said saddle; the improvement comprising means to maintain true vertical alignment of said column during movement along said ways, said means including,

(a) level sensing means carried by said column and arranged to detect level error,

(b) hydrostatic bearing means disposed between one edge of said column and said column base, and

(c) variable flow control means to actuate said hydrostatic bearing means in response to level error detected by said level sensing means whereby to tilt said column into true vertical alignment to eliminate said level error.

2. The arrangement claimed in claim 1 wherein said lifting means comprises a hydrostatic shim including (a) a shim block disposed between said edge of said column and said column base, said shim block having (i) a plurality of recesses therein, and (ii) drain means surrounding said recesses.

(b) fluid reservoir means communicating with said drain means, and

(c) means for supplying fluid under pressure from said reservoir to said recesses.

3. The arrangement claimed in claim 2 including an annular V groove near the periphery of said recess and a sealing ring having an annular wedge adapted to fit within said V groove, and means normally biasing said ring away from said V groove.

4. The arrangement claimed in claim 1 including means holding said column base against said saddle.

5. The arrangement claimed in claim 1 wherein said one edge of said column includes a flange, wherein said lifting means includes opposed hydrostatic pads bearing on the top and bottom of said flange, and wherein said means to actuate said lifting means includes a variable flow control valve controlling the flow of fluid to one of said hydrostatic pads and a reverse acting variable flow control valve controlling the flow of fluid to the other of said hydrostatic pads.

6. The arrangement claimed in claim 1 including two level sensing means arranged to detect level error in perpendicular planes, second lifting means disposed between an edge of said column perpendicular to said first mentioned edge and said column base, and means to raise and lower said second lifting means in response to level error detected by one of said level sensing means, said first mentioned means to raise and lower said lifting means being operative in response to level error detected by the other level sensing means, whereby to tilt said column into true vertical alignment,

7. In a machine tool, tilt correcting means comprising:

(a) a supporting surface;

(b) a supported surface, said surfaces having cooperating, opposed bearing surfaces;

(c) at least one recess in one of said surfaces;

(d) an annular V groove near the periphery of said recess;

(e) a sealing ring having an annular Wedge adapted to fit within said V groove, and means normally biasing said ring away from said V groove;

(f) a supply of fluid;

(g) means for supplying said fluid to said recess, said means including (i) pump means, and (ii) flow control means (h) level sensing means operative to actuate said control means; and

(i) drain means for returning said fluid to said supply.

8. The tilt correcting means claimed in claim 7 wherein said supporting surface includes a portion overlying an edge of said supported surface, said portion of said supporting surface having at least one recess, means for supplying fluid from said supply to said last mentioned recess, said means including flow control means acting oppositely to said first mentioned flow control means, said last mentioned flow control means being operative in response to said level sensing means, and drain means for returning said fluid from said second recess to said supply.

9. The tilt correcting means claimed in claim 7 including at least one additional recess in said one of said surfaces, independent means for supplying said fluid to said additional recess, said means including pump means and flow control means, and a second level sensing means operative in a plane perpendicular to said first mentioned level sensing means and operative to actuate said control means, and drain means for returning fluid from said second recess to said supply.

10. In a machine tool having a vertical column, a column base carrying said column, a saddle having a plurality of transverse ways slidably carrying said column base, and a runway having a plurality of longitudinal ways slidable carrying said saddle; the improvement comprising means to maintain true vertical alignment of said column during movement along said ways, said means including,

(a) a plurality of hydrostatic bearings disposed between said saddle and said column base,

(b) flow control means for each said hydrostatic bearing, at least one of said flow control means being variable, the remainder of said flow control means being adapted to provide a constant flow to the respective bearings,

(c) level sensing means carried by said column and arranged to detect level error, and

(d) means operatively connecting said level sensing means and said variable flow controller, whereby to tilt said column in response to level error detected by said level sensing means to maintain true vertical alignment of said column.

11. The arrangement claimed in claim 10 wherein said hydrostatic bearing having the variable flow control means includes an annular V groove near the periphery of the bearing recess, and including a sealing ring having an annular wedge adapted to fit within said V groove, and means normally biasing said ring away from said V groove.

12. The arrangement claimed in claim 10 including an additional hydrostatic bearing operative to hold said column base against said saddle, said additional hydrostatic bearing including a variable flow control valve acting oppositely to said first mentioned variable flow control valve in response to level error detected by said level sensing means.

13. In a machine tool having a vertical column, a column base carrying said column, a saddle having a plurality of transverse ways slidably carrying said column base, and a runway having a plurality of longitudinal ways slidably carrying said saddle: the improvement comprising means to maintain true vertical alignment of said column during movement along said ways, said means including,

(a) a plurality of hpdrostatic bearing pads disposed between said runway and said saddle,

(b) flow control means for each said hydrostatic hearing pad, at least one of said flow control means being variable, the remainder of said flow control means being adapted to provide a constant flow to the respective bearings,

(c) level sensing means carried by said column and arranged to detect level error,

(d) means operatively connecting said level sensing means and said variable flow controller, whereby to tilt said column into true vertical alignment.

14. The arrangement claimed in claim 13 wherein said hydrostatic bearing having the variable flow control means includes an annular V groove near the periphery of the bearing recess, and including a sealing ring having an annular wedge adapted to fit within said V groove, and means normally biasing said ring away from said V groove.

15. The arrangement claimed in claim 13 including an additional hydrostatic bearing operative to hold said column base against said saddle, said additional hydrostatic bearing including a variable flow control valve acting oppositely to said first mentioned variable flow control valve in response to level error detected by said level sensing means.

16. In a machine tool having a plurality of hydrostatic bearing pads between a supporting and a supported surface sl idable relative to each other, tilt correcting means comprising:

(a) level sensing means carried by said machine tool and operative to detect level error,

(b) variable flow control valve means operative in response to level error detected by said level sensing means to control the flow of fluid to some of said hydrostatic bearing pads; and

(c) means for supplying a constant flow of fluid to the remainder of said bearing pads.

17. In a machine tool, tilt correcting means comprising:

(a) a supporting surface;

(b) a supported surface slidable with respect to said supporting surface, said surfaces having cooperating opposed bearing faces;

(c) a plurality of recesses in one of said opposed hearing faces;

(d) a supply of fluid;

9 10 (e) means for supplying said fiuid to all said recesses, 3,008,381 11/1961 Jones 9015 said means including 3,097,568 7/ 1963 Kampmeier 248125 X (i) pump means, 3,260,162 7/1966 Atherton 9016 (ii) variable fiow control means arranged to vary 3,269,685 8/1966 Wallace 248-346 the quantity of fluid delivered to at least one of 5 3,310,263 3/ 1967 Cavanaugh 24823 said recesses, and 3,355,990 12/1967 Thum 3083.5 X (iii) constant flow control means for delivering 3,395,947 8/ 1968 Brown 3085 a constant quantity of fluid to the remainder 3,397,915 8/ 1968 Small et al 299'1 of said recesses; (f) level sensing means operative to actuate said varia- 10 ROY FRAZIER, Primary EXamiIlel' ble control means; and g) drain means for returning said fluid to said supply.

-2 1 References Cited 90 15, 48 so, 188 3, 371 30s 3 5 UNITED STATES PATENTS 15 2,648,999 8/1953 Stephan 243-23 X 2,869,933 1/1959 Bissinger 3085 

